Such automatic clutches or servo clutches are, for example, known from the text entitled "Kraftfahrtechnisches Taschenbuch", 1991 Edition, pages 538 and 539, or German patent application P 195 40 921. Servo clutches offer, in combination with electronic control apparatus, either an automated start from standstill or, together with servo-actuated shifting mechanisms, a fully automatic transmission. In such servo clutches, the disengagement and engagement of the clutch is generally actuated via a servo drive.
In addition to such servo clutches, automatic transmissions are known wherein the transmission ratios can be changed in response to a drive signal. Especially, the neutral position of the automatic transmission can be set in response to a drive signal to interrupt the force flow between the vehicle motor and the wheels. Likewise, in the case of an above-mentioned automated manual transmission, the force flow between the vehicle motor and the wheels can be interrupted by a controlled setting of the neutral position.
Such automatic transmissions can be connected via a hydraulic converter to the vehicle motor in a manner known per se. The converter can be bridged via a known converter bridge clutch in response to a drive signal or the bridge can be interrupted.
Furthermore, it is known to provide a motor control apparatus for controlling a vehicle motor. With the motor control apparatus, open-loop control or closed-loop control can be provided, for example, in dependence upon driver command, motor operating parameters and additional variables representing or influencing the operation of the vehicle. These variables can especially be the metering of fuel. In such motor controls, and for specific malfunctions, it is conventional to decrease the motor power via an emergency switchoff in a relatively short time, that is, abruptly.
A safety shutoff valve can, for example, be provided for a diesel engine so that, in the case of a fault, a safety switchoff is guaranteed. Such a safety switchoff valve is identified as ELAB for diesel engines.
German patent application 195 35 418.4 discloses that, for specific diesel injection systems such as the so-called common-rail systems, the use of such a safety shutoff valve is problematic because a large volume of fuel, which is under high pressure, is present between the safety valve and the injection nozzles. Accordingly, after actuation of the shutoff valve, the engine continues to run for a specific time or, in the case of a leak, a considerable quantity of fuel escapes under high pressure. In this application, a way is shown to reduce the engine power even more rapidly in the case of a fault.